Rinne Kudo, who is studying abroad in England, sees her classmate kidnapped by Yoko Minato right in front of her. Rinne returns to Japan with Sophia's guidance, who is investigating a series of female kidnappings, and decides to investigate the case with Girls Remix. They head to the scene of the crime with Reika Shindai to investigate a case suspected to involve an alchemist. At that moment, Yoko appears again and attacks them, but a woman who looks like Clotho appears and fights Yoko. Will Rinne be able to solve the case and save her classmates?!

Shizuka Nomura receives an invitation to a Halloween party, but no matter how many times she throws it away, it keeps coming back to her. Suspicious, Shizuka consults Akiko Narumi. Akiko infiltrates the Halloween party with the new members of the Girl Remix, Rinne Kudo and Nayuta Mikazuki! The host of the party is a surprise?! What kind of party will the Girls Remix experience?!

All the incidents occuring around the Girls Remix up to this point were part of Sumire Kurono's plan to create the ultimate Kamen Rider. Now that plan is moving into its final phase. Sumire kidnapes Nayuta Mikazuki again. After performing her final surgery, "Kamen Rider Eins" is finally born. Will the Girls Remix be able to get Nayuta back? And what will become of Nayuta, who has become Kamen Rider Eins?

Nayuta always wanted to be stronger and more beautiful than anyone else since she was a child. However, her greed is sinful, and she views it as weakness and ugliness, locking it away in her heart. Then, an incident occurs that shakes her destiny. Witness the birth of Kamen Rider Eins from a unique perspective.

A special that acts as a prelude to Kamen Rider Eins with Girls Remix.